1. Field of the Invention
The present invention relates in general to device for assembling of an optical fiber connector connecting two optical fibers for using these fibers in optical communication and, more particularly, to a rotation and alignment device for assembling of an optical fiber connector connecting single-mode optical fibers with a lower connection loss.
2. Description of the Prior Art
Conventionally, in order to practically use optical fibers, for example, single-mode optical fibers, in an optical communication, these optical fibers should be precisely connected to each other using an optical fiber connector such that their centers are precisely aligned with each other. As well known to those skilled in the art, the optical fiber connection using an optical fiber connector is achieved by inserting and fixing the optical fibers in individual precise ferrules. These ferrules are in turn polished together with the end surfaces of their optical fibers such that the end surfaces of the fibers are perpendicular to the fiber axis. The ferrules having individual optical fibers are, thereafter, precisely aligned with each other by a precisely machined sleeve such that the ends of their optical fibers are precisely aligned with and connected to each other. Upon accomplishing the precise alignment and connection of the optical fibers by the optical fiber connector, these optical fibers can transmit optical signals therethrough in order to achieve the desired optical communication. Here, a desired connection between the two optical fibers of the same kind is achieved when it assures ideal continuity of optical waveguide medium, thus to achieve a perfect optical communication with no signal loss.
There will be no connection loss or no signal loss of the optical fiber connector when all the parts, such as the ferrules, the sleeve and the optical fibers, of the optical fiber connector are geometrically perfectly fabricated and assembled into the optical connector. However, the conventional optical fiber connector inevitably generates a connection loss or a signal loss at about the connecting portion of the optical fibers since the optical fiber connection using the connector practically introduces varieties of factors of incomplete connection.
The connection loss or the signal loss of the optical fiber connection using the conventional optical fiber connector are caused by optical fiber misalignments which are generally classified into two types, that is, extrinsic misalignments and intrinsic misalignments. Here, it is noted that improvement or reduction of the intrinsic misalignments of the optical fibers is very difficult such that it is scarcely achieved. In this regard, the recent approaches to development and production of optical fiber connectors showing a desired level of connection loss are concentrated to improvement or reduction of the extrinsic misalignments other than the intrinsic misalignments.
The extrinsic misalignments introduced in fiber connection using an optical fiber connector are generally classified into three types, that is, a gap misalignment between the facing ends of the two optical fibers, a lateral misalignment caused by the axial misalignment of the centers of the optical fibers and an angular misalignment caused by bending of the optical fibers. It is particularly noted that the connection loss introduced in the fiber connection of the single-mode optical fibers using the optical connector is mostly influenced by the lateral misalignment of the three extrinsic misalignments. This means that the development and production of an optical fiber connector showing the desired level of connection loss can be achieved by appropriate reduction of the three extrinsic misalignments, which trade off with each other, and, more particularly, by appropriate reduction of the lateral misalignment. Here, it should be noted that the endless approach to precision of all the parts of the optical fiber connector for reduction of the connection loss is attended with undesirable increase of cost of the optical fiber connector, thus to be insufficient in a competitive price and to cause a difficulty in production of the optical connector on a commercial scale.
In recent, there have been several proposals for optical connector assembling technique and for development of optical connector assembling system each of which provides an optical fiber connector showing a desirably lower connection loss when the parts of the optical fiber connector, produced with such appropriate precision that no serious increase of cost is caused, are assembled into the optical fiber connector connecting the optical fibers to each other. Particularly, it is noted that a SC-type optical fiber connector results in a good effect of reduction of the connection loss by appropriate rotational adjustment of the centers of the optical fibers, which are connected to each other together with their ferrules in the sleeve, instead of fixing the centers of the optical fibers at a given alignment position.
In the optical fiber connection using the SC-type optical connector, two ferrules previously coupled to individual optical fibers are used. That is, a light beam of a light source is received by an end of an optical fiber of a stationary ferrule while a corresponding end of an optical fiber of the other ferrule or a movable ferrule is provided with an optical powermeter. In this fiber connection, the movable ferrule is rotated with respect to the stationary ferrule until the optical powermeter detects the most intensive optical power. Here, the lateral misalignment of the optical fibers of the ferrules in the sleeve is most reduced when the optical powermeter detects the most intensive optical power.
However, the desired reduction of lateral misalignment of the optical fibers in the optical fiber connection using the SC-type optical connector is achieved not by direct finding and alignment of the centers of the optical fibers in the sleeve but by rotational adjustment of the movable ferrule with respect to the stationary ferrule in order to indirectly align the centers of the optical fibers in a predetermined alignment region using change of the optical power transmission effect. Hence, the above optical fiber connection using the SC-type optical connector has a problem that it is required to rotate several times the movable ferrule with respect to the stationary ferrule in order to detect the most intensive optical power and to align the centers of the optical fibers in the predetermined alignment region. Another problem of the optical fiber connection using the SC-type optical connector is resided in that it requires much time in order to achieve the desired alignment of the centers of the optical fibers particularly when the predetermined alignment region is defined to be such narrower that optimal reduction of the connection loss can be achieved. Hence, this optical fiber connection using the SC-type connector still causes a difficulty in minimization of the connection loss.